The black cat, also called the "wild cat" or "sabot-cat", usually with an arched back and with claws and teeth bared, is closely associated with anarchism, especially with anarcho-syndicalism. It was designed by Ralph Chaplin, who was a prominent figure in the Industrial Workers of the World (IWW). As its aggressive stance suggests, the cat is meant to suggest such ideas as wildcat strikes, sabotage, and radical unionism.
The origin of the black cat symbol is unclear, but according to one story it came from a IWW strike that was going badly. Several members had been beaten up and were put in a hospital. At that time a skinny, black cat walked into the striker's camp. The cat was fed by the striking workers and as the cat regained its health the strike took a turn for the better. Eventually the striking workers got some of their demands and they adopted the cat as their mascot.